Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$232.62	5.704%	$245.8886	$245.89	$245.90	$245.90
Purchase #2	$150.83	8.718%	$163.9794	$163.98	$164.00	$164.00
Purchase #3	$87.86	10.372%	$96.9728	$96.97	$96.95	$97.00
Purchase #4	$18.29	3.291%	$18.8919	$18.89	$18.90	$18.90
Purchase #5	$183.57	13.722%	$208.7595	$208.76	$208.75	$208.80
Purchase #6	$103.68	7.324%	$111.2735	$111.27	$111.25	$111.30
Purchase #7	$96.91	3.776%	$100.5693	$100.57	$100.55	$100.60
7 purchase totals =	$873.76		$946.3350	$946.33	$946.30	$946.50